skbuff: move __alloc_skb() next to the other skb allocation functions

In preparation before reusing several functions in all three skb
allocation variants, move __alloc_skb() next to the
__netdev_alloc_skb() and __napi_alloc_skb().
No functional changes.
Signed-off-by: NAlexander Lobakin <alobakin@pm.me>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -119,148 +119,6 @@ static void skb_under_panic(struct sk_buff *skb, unsigned int sz, void *addr)
 	skb_panic(skb, sz, addr, __func__);
 }
 
-/*
- * kmalloc_reserve is a wrapper around kmalloc_node_track_caller that tells
- * the caller if emergency pfmemalloc reserves are being used. If it is and
- * the socket is later found to be SOCK_MEMALLOC then PFMEMALLOC reserves
- * may be used. Otherwise, the packet data may be discarded until enough
- * memory is free
- */
-#define kmalloc_reserve(size, gfp, node, pfmemalloc) \
-	 __kmalloc_reserve(size, gfp, node, _RET_IP_, pfmemalloc)
-
-static void *__kmalloc_reserve(size_t size, gfp_t flags, int node,
-			       unsigned long ip, bool *pfmemalloc)
-{
-	void *obj;
-	bool ret_pfmemalloc = false;
-
-	/*
-	 * Try a regular allocation, when that fails and we're not entitled
-	 * to the reserves, fail.
-	 */
-	obj = kmalloc_node_track_caller(size,
-					flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
-					node);
-	if (obj || !(gfp_pfmemalloc_allowed(flags)))
-		goto out;
-
-	/* Try again but now we are using pfmemalloc reserves */
-	ret_pfmemalloc = true;
-	obj = kmalloc_node_track_caller(size, flags, node);
-
-out:
-	if (pfmemalloc)
-		*pfmemalloc = ret_pfmemalloc;
-
-	return obj;
-}
-
-/* 	Allocate a new skbuff. We do this ourselves so we can fill in a few
- *	'private' fields and also do memory statistics to find all the
- *	[BEEP] leaks.
- *
- */
-
-/**
- *	__alloc_skb	-	allocate a network buffer
- *	@size: size to allocate
- *	@gfp_mask: allocation mask
- *	@flags: If SKB_ALLOC_FCLONE is set, allocate from fclone cache
- *		instead of head cache and allocate a cloned (child) skb.
- *		If SKB_ALLOC_RX is set, __GFP_MEMALLOC will be used for
- *		allocations in case the data is required for writeback
- *	@node: numa node to allocate memory on
- *
- *	Allocate a new &sk_buff. The returned buffer has no headroom and a
- *	tail room of at least size bytes. The object has a reference count
- *	of one. The return is the buffer. On a failure the return is %NULL.
- *
- *	Buffers may only be allocated from interrupts using a @gfp_mask of
- *	%GFP_ATOMIC.
- */
-struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
-			    int flags, int node)
-{
-	struct kmem_cache *cache;
-	struct skb_shared_info *shinfo;
-	struct sk_buff *skb;
-	u8 *data;
-	bool pfmemalloc;
-
-	cache = (flags & SKB_ALLOC_FCLONE)
-		? skbuff_fclone_cache : skbuff_head_cache;
-
-	if (sk_memalloc_socks() && (flags & SKB_ALLOC_RX))
-		gfp_mask |= __GFP_MEMALLOC;
-
-	/* Get the HEAD */
-	skb = kmem_cache_alloc_node(cache, gfp_mask & ~__GFP_DMA, node);
-	if (!skb)
-		goto out;
-	prefetchw(skb);
-
-	/* We do our best to align skb_shared_info on a separate cache
-	 * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives
-	 * aligned memory blocks, unless SLUB/SLAB debug is enabled.
-	 * Both skb->head and skb_shared_info are cache line aligned.
-	 */
-	size = SKB_DATA_ALIGN(size);
-	size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-	data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc);
-	if (!data)
-		goto nodata;
-	/* kmalloc(size) might give us more room than requested.
-	 * Put skb_shared_info exactly at the end of allocated zone,
-	 * to allow max possible filling before reallocation.
-	 */
-	size = SKB_WITH_OVERHEAD(ksize(data));
-	prefetchw(data + size);
-
-	/*
-	 * Only clear those fields we need to clear, not those that we will
-	 * actually initialise below. Hence, don't put any more fields after
-	 * the tail pointer in struct sk_buff!
-	 */
-	memset(skb, 0, offsetof(struct sk_buff, tail));
-	/* Account for allocated memory : skb + skb->head */
-	skb->truesize = SKB_TRUESIZE(size);
-	skb->pfmemalloc = pfmemalloc;
-	refcount_set(&skb->users, 1);
-	skb->head = data;
-	skb->data = data;
-	skb_reset_tail_pointer(skb);
-	skb->end = skb->tail + size;
-	skb->mac_header = (typeof(skb->mac_header))~0U;
-	skb->transport_header = (typeof(skb->transport_header))~0U;
-
-	/* make sure we initialize shinfo sequentially */
-	shinfo = skb_shinfo(skb);
-	memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
-	atomic_set(&shinfo->dataref, 1);
-
-	if (flags & SKB_ALLOC_FCLONE) {
-		struct sk_buff_fclones *fclones;
-
-		fclones = container_of(skb, struct sk_buff_fclones, skb1);
-
-		skb->fclone = SKB_FCLONE_ORIG;
-		refcount_set(&fclones->fclone_ref, 1);
-
-		fclones->skb2.fclone = SKB_FCLONE_CLONE;
-	}
-
-	skb_set_kcov_handle(skb, kcov_common_handle());
-
-out:
-	return skb;
-nodata:
-	kmem_cache_free(cache, skb);
-	skb = NULL;
-	goto out;
-}
-EXPORT_SYMBOL(__alloc_skb);
-
 /* Caller must provide SKB that is memset cleared */
 static struct sk_buff *__build_skb_around(struct sk_buff *skb,
 					  void *data, unsigned int frag_size)
@@ -408,6 +266,148 @@ void *__netdev_alloc_frag_align(unsigned int fragsz, unsigned int align_mask)
 }
 EXPORT_SYMBOL(__netdev_alloc_frag_align);
 
+/*
+ * kmalloc_reserve is a wrapper around kmalloc_node_track_caller that tells
+ * the caller if emergency pfmemalloc reserves are being used. If it is and
+ * the socket is later found to be SOCK_MEMALLOC then PFMEMALLOC reserves
+ * may be used. Otherwise, the packet data may be discarded until enough
+ * memory is free
+ */
+#define kmalloc_reserve(size, gfp, node, pfmemalloc) \
+	 __kmalloc_reserve(size, gfp, node, _RET_IP_, pfmemalloc)
+
+static void *__kmalloc_reserve(size_t size, gfp_t flags, int node,
+			       unsigned long ip, bool *pfmemalloc)
+{
+	void *obj;
+	bool ret_pfmemalloc = false;
+
+	/*
+	 * Try a regular allocation, when that fails and we're not entitled
+	 * to the reserves, fail.
+	 */
+	obj = kmalloc_node_track_caller(size,
+					flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
+					node);
+	if (obj || !(gfp_pfmemalloc_allowed(flags)))
+		goto out;
+
+	/* Try again but now we are using pfmemalloc reserves */
+	ret_pfmemalloc = true;
+	obj = kmalloc_node_track_caller(size, flags, node);
+
+out:
+	if (pfmemalloc)
+		*pfmemalloc = ret_pfmemalloc;
+
+	return obj;
+}
+
+/* 	Allocate a new skbuff. We do this ourselves so we can fill in a few
+ *	'private' fields and also do memory statistics to find all the
+ *	[BEEP] leaks.
+ *
+ */
+
+/**
+ *	__alloc_skb	-	allocate a network buffer
+ *	@size: size to allocate
+ *	@gfp_mask: allocation mask
+ *	@flags: If SKB_ALLOC_FCLONE is set, allocate from fclone cache
+ *		instead of head cache and allocate a cloned (child) skb.
+ *		If SKB_ALLOC_RX is set, __GFP_MEMALLOC will be used for
+ *		allocations in case the data is required for writeback
+ *	@node: numa node to allocate memory on
+ *
+ *	Allocate a new &sk_buff. The returned buffer has no headroom and a
+ *	tail room of at least size bytes. The object has a reference count
+ *	of one. The return is the buffer. On a failure the return is %NULL.
+ *
+ *	Buffers may only be allocated from interrupts using a @gfp_mask of
+ *	%GFP_ATOMIC.
+ */
+struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
+			    int flags, int node)
+{
+	struct kmem_cache *cache;
+	struct skb_shared_info *shinfo;
+	struct sk_buff *skb;
+	u8 *data;
+	bool pfmemalloc;
+
+	cache = (flags & SKB_ALLOC_FCLONE)
+		? skbuff_fclone_cache : skbuff_head_cache;
+
+	if (sk_memalloc_socks() && (flags & SKB_ALLOC_RX))
+		gfp_mask |= __GFP_MEMALLOC;
+
+	/* Get the HEAD */
+	skb = kmem_cache_alloc_node(cache, gfp_mask & ~__GFP_DMA, node);
+	if (!skb)
+		goto out;
+	prefetchw(skb);
+
+	/* We do our best to align skb_shared_info on a separate cache
+	 * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives
+	 * aligned memory blocks, unless SLUB/SLAB debug is enabled.
+	 * Both skb->head and skb_shared_info are cache line aligned.
+	 */
+	size = SKB_DATA_ALIGN(size);
+	size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc);
+	if (!data)
+		goto nodata;
+	/* kmalloc(size) might give us more room than requested.
+	 * Put skb_shared_info exactly at the end of allocated zone,
+	 * to allow max possible filling before reallocation.
+	 */
+	size = SKB_WITH_OVERHEAD(ksize(data));
+	prefetchw(data + size);
+
+	/*
+	 * Only clear those fields we need to clear, not those that we will
+	 * actually initialise below. Hence, don't put any more fields after
+	 * the tail pointer in struct sk_buff!
+	 */
+	memset(skb, 0, offsetof(struct sk_buff, tail));
+	/* Account for allocated memory : skb + skb->head */
+	skb->truesize = SKB_TRUESIZE(size);
+	skb->pfmemalloc = pfmemalloc;
+	refcount_set(&skb->users, 1);
+	skb->head = data;
+	skb->data = data;
+	skb_reset_tail_pointer(skb);
+	skb->end = skb->tail + size;
+	skb->mac_header = (typeof(skb->mac_header))~0U;
+	skb->transport_header = (typeof(skb->transport_header))~0U;
+
+	/* make sure we initialize shinfo sequentially */
+	shinfo = skb_shinfo(skb);
+	memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
+	atomic_set(&shinfo->dataref, 1);
+
+	if (flags & SKB_ALLOC_FCLONE) {
+		struct sk_buff_fclones *fclones;
+
+		fclones = container_of(skb, struct sk_buff_fclones, skb1);
+
+		skb->fclone = SKB_FCLONE_ORIG;
+		refcount_set(&fclones->fclone_ref, 1);
+
+		fclones->skb2.fclone = SKB_FCLONE_CLONE;
+	}
+
+	skb_set_kcov_handle(skb, kcov_common_handle());
+
+out:
+	return skb;
+nodata:
+	kmem_cache_free(cache, skb);
+	skb = NULL;
+	goto out;
+}
+EXPORT_SYMBOL(__alloc_skb);
+
 /**
  *	__netdev_alloc_skb - allocate an skbuff for rx on a specific device
  *	@dev: network device to receive on